Natural killer cell cytotoxicity: a methods analysis of 51chromium release versus flow cytometry

The purpose of this study is to describe design considerations for the use of flow cytometry (FC) compared to 51chromium (51Cr)-release assays utilizing cryopreserved peripheral blood mononuclear cells (PBMCs) to detect natural killer (NK) cell cytotoxicity. Subjects were 10 healthy women aged 18 to 39 years. Intra-assay variability between methods differed only at the lowest effector-target ratios evaluated. Interassay variability was wide but did not differ between methods. The relationship of lytic unit-10 between methods was strongly positive. Cytotoxicity detected by 51Cr release was higher than that detected by FC for all 10 subjects. Cost was comparable. However, had more assays been performed, technician time would have been greater with flow cytometry. More whole blood was needed to perform the flow cytometry cytotoxicity assay than 51Cr-release cytotoxicity assay. The authors found no compelling reason to adopt NK cell cytotoxicity by flow cytometry over 51Cr release.